They have already seen a high number of reported cases in the first two months of 2011, when dengue should be fairly dormant. Alarm is also being raised by the number of patients suffering from dengue hemorrhagic fever (around two-thirds, compared to half in 2010). Major outbreaks of dengue fever strike Cambodia every 3 to 5 years and in interviews given to IRIN, specialists at the NDCP are saying the pattern of cases is looking similar to 2007, when the last large epidemic hospitalised around 40,000 people, with over 10,000 in one week.
Cambodia normally takes measures each year to try and reduce cases of dengue during what’s known as the ‘nightmare season’. However, this year there could be problems in the implementation of these programmes. An annual grant which normally makes up three-fifths of the NDCP’s budget is yet to arrive from the Asian Development Bank. And since Cambodia’s health services were decentralised three years ago, there is uncertainty over what control measures are being taken in certain areas and whether provinces have begun distribution of the chemical used to kill mosquito larvae.
Recent research from Peru (where a dengue outbreak killed 14 people earlier this year) questions whether this is the most effective technique for controlling the spread of dengue fever. Researchers found that mosquitoes choose to lay their eggs in water which is already heavily infested with those of other mosquitoes. Therefore using larvicides to kill eggs or removing them, may simply spur mosquitoes to find other sites. Instead, the creation of ‘egg-sinks’ treated with growth regulators to limit the emergence of adults may be a better way to control mosquito numbers, though the scientists warn that individual countries may need to adopt different controlling strategies.
In recent years, the NDCP has tried alternative methods in Cambodia for preventing dengue, such as introducing guppy fish (which eat mosquito larvae) in water storage containers. These trial projects have been ongoing for 7 years and have prevented serious outbreaks of dengue. But though this kind of scheme only costs around 1 dollar per household to maintain, up-front investment is needed to put the necessary infrastructure in place. Wider adoption is therefore prevented by the short-term nature of many aid grants.
According to a spokesperson at the World Health Organisation (WHO) in Cambodia, there is currently no alarm within the organisation over reported cases of dengue fever in 2011. However, he admitted that the situation could change.